For well over a century, the public has relied upon the bank safe deposit vault as a reliable receptacle for their valuables of jewelry, negotiable securities and other items. Banks are proud to provide this service in which security is the result of the vault being of reinforced concrete with a secure door, time locks, and various other security measures. Well known to the bank customer is the feature that a box of the appropriate size for their needs is available and access is limited to banking hours where only authorized persons with a proper key can reach the box when trusted bank personnel provide and use a second key to open the box protecting door. The customer may then have access to the box which is removable to a private booth in which the customer may add or remove contents. There is no record of the contents of the box since this is a private matter of the box renter.
The bank, in providing boxes of several sizes, will maintain in the vault modules of different size boxes, for example, a module containing four large boxes each having approximately 3 cubic feet of storage space, to the smallest boxes in a module containing as many as 28 boxes each having a storage space in the order of 1/6 cubic foot, sufficient to hold a number of documents 6 inches by 12 inches in size, common dimensions for securities with space left over for other valuables.
The modules are of various sizes, for example, 24 inches by 24 inches and 12 inches by 24 inches in front, and have a common depth of approximately 26 inches to provide a uniform front surface. The modules, because of their heavy double lock doors in front, interior sturdy box and enclosure for each box behind the door are surprisingly heavy, being in the order of 100 pounds each when empty. Modules are usually stacked to a height of approximately 6' from the floor. The weight of a stack of modules is not a problem since the vault has a reinforced floor capable of holding much more than the weight of many modules even if filled with jewelry or bullion.
The modules are normally stacked to within a few inches of the vault ceiling and placed in rows with 3 to 4 feet spacing between the rows. Normally, safe deposit vaults are accessed by a single customer with a single bank representative at a time, so the corridors need not be large. More stacks of modules may therefore be contained in a vault. In most cases the weight of the modules has been considered to be sufficient to provide a column of boxes which are perfectly safe from movement.
Recently, however, it is recognized that from the structural standpoint, the stacks of modules may move, tip or fall under such conditions as seismic activity. It has likewise been learned that even the dual lock doors may not hold boxes in place in a module if the module falls. The integrity of individual boxes under such conditions is the sole protection against the contents of boxes being commingled. Of even greater importance, if someone is present in the vault at the time of some seismic activity or other action, such as bank personnel rearranging or adding additional modules which could cause a module to fall, there is real danger to the persons present in the vault.
We have also discovered that there appears to be little standardization among different manufacturers of safe deposit boxes in their dimensions except as to depth and box dimensions. Banks have acquired modules from different manufactures and stacked them in intermixed arrangements. Therefore, the height of various modules may vary. Likewise, vaults may have different floor to ceiling dimensions. These variations in configuration usually result in compromise to the stability of intermixed safe deposit boxes.